Delete all in rails console

i have an association for a user as user has_many agents and agent belongs_to user. in rails console,i am trying to use different users to test a particular scenario and i want a user with no agents,hence i want to delete the user.agents. i tried user.agents.map(&:destroy),but it gives error as ActiveRecord::StaleObjectError: Attempted to delete a stale object.i even tried user.agents.delete_all but it too does not work.can i delete the users agents with a single command in rails console.